TWI518169B - A method for producing β -sialon - Google Patents

Description

Method for producing β-type lanthanum aluminum oxynitride

The present invention relates to a method for producing a β-type lanthanum aluminum oxynitride which can be utilized as a phosphor which can be used in a light-emitting device using a blue light-emitting diode or an ultraviolet light-emitting diode.

The temporarily synthesized β-type lanthanum aluminum oxynitride is heated in a vacuum or an inert gas atmosphere with a low partial pressure of nitrogen, and the brightness of the β-type lanthanum aluminum oxynitride is significantly improved by performing heat treatment and acid treatment (patent Document 1).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] International Publication No. 2008/062781

It is an object of the present invention to provide a method for producing a beta-type lanthanum aluminum oxynitride having a higher fluorescence intensity.

The present invention provides a method for producing a β-type lanthanum aluminum oxynitride, which is a method for producing a β-type lanthanum aluminum oxynitride phosphor having a step of mixing a raw material containing cerium, aluminum and lanthanum. Powder mixing; a calcination step of calcining a raw material obtained by mixing in an inert gas or a non-oxidizing gas to form a general formula: Si _6-z Al _z O _z N _8-z :Eu (β<z<4.2) β-type lanthanum aluminum oxynitride; an annealing step of annealing the generated β-type lanthanum aluminum oxynitride; and an acid treatment step, which is annealed The β-type lanthanum aluminum oxynitride is immersed in an acid solution; the annealing treatment is performed under a reducing gas atmosphere, the gas ambient pressure is 1 kPa or more and 10 MPa or less, the gas ambient temperature is 1200 ° C or more and 1600 ° C or less, and the treatment time is 1 hour or more and 24 hours or less. .

The reducing gas atmosphere is preferably hydrogen. The reducing gas atmosphere is preferably a mixed gas of a reducing gas and an inert gas, and the hydrogen concentration in the mixed gas is preferably 1% by volume or more.

Preferably, the acid solution of the acid treatment step is a mixed acid containing at least hydrofluoric acid and nitric acid.

The firing is preferably carried out in a gas atmosphere at a temperature of 1850 ° C or higher.

The present invention utilizes a method for producing β-type lanthanum aluminum oxynitride to obtain β-type yttrium aluminum having higher fluorescence intensity by controlling the kind of gas environment in the annealing step, its pressure and temperature, and the treatment time. Nitrogen oxides.

The present invention relates to a method for producing a β-type lanthanum aluminum oxynitride, which has the following steps: a mixing step of mixing raw material powders containing cerium, aluminum and cerium; and a firing step, which is a raw material obtained by mixing The firing is carried out in a gas atmosphere of an inert gas or a non-oxidizing gas to form a β-type lanthanum-aluminum nitrogen represented by a general formula: Si _6-z Al _z O _z N _8-z :Eu (0<z<4.2). An oxide; and an annealing step of annealing the sintered β-type lanthanum aluminum oxynitride, and the annealing treatment is performed under a reducing gas atmosphere of a pressurized gas atmosphere of 1 kPa or more to a pressurized gas atmosphere of 10 MPa. The gas ambient temperature is 1200 ° C or higher and 1600 ° C or lower, and the treatment time is 1 hour or longer and 24 hours or shorter.

When the temperature of the gas atmosphere in the firing step is lower than 1800 ° C, sufficient fluorescence intensity may not be easily supplied. Therefore, the temperature of the gas atmosphere at the time of firing is preferably 1850 ° C or higher.

The reason why the gas atmosphere in the annealing step is formed into a reducing gas environment is because the reducing gas acts on the crystal defects in which the electrical neutrality of the β-type lanthanum oxynitride is not locally maintained, and the crystallinity is improved. Therefore. As the crystallinity increases, the fluorescence intensity of the β-type lanthanum aluminum oxynitride increases.

The reducing gas system contains any monomer or mixture of ammonia gas, hydrocarbon gas, carbon monoxide gas, and hydrogen gas, and hydrogen gas having a smaller molecular size is more effective for improving crystallinity, which is preferable.

The reducing gas can also be mixed with an inert gas. The inert gas system refers to a rare gas or nitrogen of the element of Group 18 of the periodic table, and in the case of a rare gas, argon or helium is listed. When the reducing gas atmosphere is a mixed gas and the reducing gas in the mixed gas is hydrogen, if the concentration of the reducing gas in the mixed gas is too low, the crystallinity is hard to be improved. Therefore, it is preferably 1% by volume or more.

The characteristic improvement effect in the annealing step is exerted under a wide range of gas ambient pressures under reduced pressure to pressurization, but the pressure lower than 1 kPa is less effective due to the gas environment, and the characteristics are less likely to be improved, and It is less desirable because it promotes the decomposition of β-type lanthanum aluminum oxynitride. In addition, by pressurizing the gas environment, other conditions required for the annealing effect can be expanded (low temperature, time shortening), but even if the gas ambient pressure is too high, the annealing effect is reached, and it is necessary to have A special and expensive annealing device, therefore, in consideration of mass productivity, a preferred gas ambient pressure is 10 MPa or less, more preferably less than 1 MPa.

If the gas ambient temperature in the annealing step is too low, the crystallinity improving effect is lowered. If the temperature is too high, the β-type lanthanum aluminum oxynitride decomposes, so it is 1200 ° C or more and 1600 ° C or less.

If the treatment time in the annealing step is too short, the effect of improving the crystallinity is low. If the treatment time is too long, the annealing effect is reached. Therefore, it is 1 hour or more and 24 hours or less, preferably 2 hours or more and 10 hours or less.

After the annealing step described above, an acid treatment step of immersing the β-type lanthanum aluminum oxynitride in the acid solution is performed, thereby further improving the characteristics of the phosphor.

Preferably, the acid treatment step comprises: impregnating the β-type lanthanum aluminum oxynitride in the acid solution, separating the β-type lanthanum aluminum oxynitride from the acid by a filter or the like, and washing the separated β-type lanthanum aluminum oxynitride by water. step. By the acid treatment, the decomposition product of the β-type lanthanum aluminum oxynitride crystal which is generated during the annealing step can be removed, thereby improving the fluorescence characteristics. The acid to be used for the acid treatment is preferably a monomer or a mixture of hydrofluoric acid, sulfuric acid, phosphoric acid, hydrochloric acid, or nitric acid, and preferably contains a mixed acid of hydrofluoric acid and nitric acid suitable for removing the decomposition product. The temperature of the acid solution during the acid treatment may be room temperature. However, in order to enhance the effect of the acid treatment, it is preferably heated to 50° C. or higher and 90° C. or lower.

Since the ?-type lanthanum aluminum oxynitride after the firing step is in the form of a block, it is preferred to carry out cracking, pulverization, and, if necessary, a classification operation to form a powder having a predetermined size. In order to suitably use the ?-type lanthanum aluminum oxynitride as the white LED phosphor, it is preferred to form the average particle diameter to 6 to 30 μm. The step of adjusting the average particle diameter of the ?-type lanthanum aluminum oxynitride may be carried out at any time after the firing step of the present invention, after the annealing step, and after the acid treatment step.

[Examples]

An embodiment of the present invention will be described in detail with reference to a comparative example.

In this embodiment, a mixing step is performed in which a raw material powder containing cerium, aluminum, and cerium is mixed; and a firing step is performed in a gas atmosphere in which an inert gas or a non-oxidizing gas is mixed. Performing calcination to form a β-type lanthanum aluminum oxynitride represented by a general formula: Si _6-z Al _z O _z N _8-z :Eu (0<z<4.2); and an annealing step, which is to be fired The formed β-type lanthanum aluminum oxynitride is annealed.

<mixing step>

In the mixing step, α-type tantalum nitride (manufactured by Ube Industries Co., Ltd., SN-E10 grade, oxygen content: 1.0% by mass) and aluminum nitride powder (Foku grade made by Tokuyama Co., Ltd., oxygen content 0.8) were mixed. Mass %), a step of alumina powder (TM-DAR grade manufactured by Daming Chemical Co., Ltd.), and yttrium oxide powder (RU grade manufactured by Shin-Etsu Chemical Co., Ltd.). The blending ratio at the time of mixing is in the general formula of β-type lanthanum oxynitride: Si _6-z Al _z O _z N _8-z , except for yttrium oxide, which is designed to be z=0.24, and the yttrium oxide system is formed as 0.8% by mass of the entire raw material.

In the mixing step, the raw material powders were mixed by a wet ball mill using ethanol as a solvent using a can and a cup made of tantalum nitride. After mixing, the solvent was removed and dried, and then the aggregate was removed by passing through a sieve having a mesh opening of 150 μm to obtain a raw material.

<Burning step>

In the firing step, the obtained raw material is filled in a cylindrical cylindrical boron nitride container (N-1 grade manufactured by Electric Chemical Industry Co., Ltd.), and the electric furnace of the carbon heater is added at 0.85 MPa. In a nitrogen gas atmosphere, β-type lanthanum aluminum oxynitride was formed by placing it in an environment of 2000 ° C for 14 hours.

The produced β-type lanthanum aluminum oxynitride is a thin aggregated block. Therefore, the generated β-type lanthanum aluminum oxynitride was slightly cracked, and then formed into a powder by pyrolysis by a supersonic jet mill (manufactured by Nippon Pneumatic Mfg. Co., PJM-80SP). shape.

< annealing step>

In the annealing step, β-type lanthanum aluminum oxynitride is filled in a cylindrical boron nitride container, and an electric furnace made of a metal (the furnace inner member is composed of a high melting point metal of tungsten and molybdenum) is used in the furnace of the tungsten heater. Come on. After the β-type lanthanum aluminum oxynitride is placed in the electric furnace, the electric furnace is evacuated to 5 Pa or less, and the temperature is raised to 1000 ° C at 20 ° C/min under vacuum, and then hydrogen gas is introduced into the electric furnace to electrically The inside of the furnace was formed to be 0.15 MPa. Further, hydrogen gas was introduced into the electric furnace, and when the gas ambient pressure was kept constant, the temperature was directly raised to 1500 ° C at 5 ° C / min, and maintained at 1500 ° C for 4 hours, after which the inside of the electric furnace was cooled to room temperature.

<acid treatment step>

The acid treatment is carried out on an annealed β-type lanthanum aluminum oxynitride in an acid solution of a mixed acid of hydrofluoric acid and nitric acid. The temperature of the acid solution was set to 70 °C. The acid-treated β-type lanthanum aluminum oxynitride is precipitated, the supernatant liquid and the fine powder are removed, distilled water is added, stirred and allowed to stand, and decantation of the supernatant and the fine powder is repeatedly performed until the solution becomes The β-type lanthanum aluminum oxynitride of Example 1 was obtained by filtration and drying of the finally obtained precipitate.

The obtained β-type lanthanum aluminum oxynitride was subjected to powder X-ray diffraction (XRD) measurement using a Kα line of Cu, and the crystal phase was a β-type lanthanum aluminum oxynitride single phase. The average particle diameter determined by the particle size distribution measuring apparatus by the laser diffraction scattering method was 13.5 μm.

The fluorescence characteristics of the β-type lanthanum aluminum oxynitride of Example 1 were measured by measuring the fluorescence spectrum in blue light excitation (wavelength 455 nm) by using a spectrofluorometer (F7000) manufactured by Hitachi Advanced Technology Co., Ltd. The obtained fluorescence spectrum is shown in Fig. 1.

The peak value in each condition and the fluorescence intensity was taken as the fluorescence peak intensity and is shown in Table 1.

It is preferable that the gas atmosphere in the annealing step is preferably a gas atmosphere pressure of 1 kPa or more, a gas atmosphere temperature of 1200 ° C or more and 1600 ° C or less, and a treatment time of 1 hour or more and 24 hours or less in a reducing gas atmosphere containing a reducing gas. The gaseous environment is hydrogen.

(Comparative Example 1)

In Comparative Example 1, a β-type lanthanum aluminum oxynitride was produced by the same method as in Example 1 except that the annealing gas atmosphere was formed into argon gas. As a result of XRD measurement, the crystal phase was a β-type lanthanum aluminum oxynitride single phase, and the average particle diameter determined by the above-described particle size distribution measuring apparatus was 13.8 μm.

The fluorescence spectrum measured by the same method as that of Example 1 about the obtained β-type lanthanum aluminum oxynitride is shown in Fig. 1 . Since the fluorescence spectrum was changed depending on the measurement apparatus or the conditions, the measurement was carried out under the same conditions as in Example 1 except that the measurement in Example 1 was not separated. As shown in Fig. 1, the fluorescence intensity is improved by forming a gas atmosphere in the annealing treatment after firing into reducing hydrogen gas.

(Comparative Examples 2 and 3)

In Comparative Example 2, β-type lanthanum aluminum oxynitride was produced in the same manner as in Example 1 except that the gas ambient pressure in the annealing step was set to 0.5 kPa of less than 1 kPa. In Comparative Example 3, a β-type lanthanum aluminum oxynitride was produced in the same manner as in Example 1 except that the temperature in the annealing step was changed to 1,650 ° C which was more than 1600 ° C. Either of them partially decomposes the ?-type lanthanum aluminum oxynitride in the annealing step, and the fluorescence characteristics are largely lowered.

(Examples 2 to 5)

In Examples 2 to 5, β-type lanthanum aluminum oxynitride was produced under the same conditions as in Example 1 except for the contents shown in Table 1.

The peak intensity of the fluorescence in Examples 2 to 5 was higher than that of Comparative Example 1.

Although not described in the table, when the reducing gas of the first embodiment is replaced with each of ammonia gas, hydrocarbon gas, and carbon monoxide gas, β-type lanthanum aluminum nitride having a fluorescence spectrum substantially the same as that of the first embodiment can be produced. Oxide.

[Industrial availability]

The β-type lanthanum aluminum oxynitride obtained by the present invention is excited by a wide wavelength range of ultraviolet to blue light, exhibiting high-luminance green light, and thus can be used as a fluorescent light of a white LED as a blue or ultraviolet light source. Appropriate use.

Fig. 1 is a view showing a fluorescence spectrum obtained by external excitation light of a wavelength of 455 nm in Example 1 and Comparative Example 1.

Claims (5)

A method for producing a β-type lanthanum aluminum oxynitride, which is a method for producing a β-type lanthanum aluminum oxynitride phosphor having a step of mixing a raw material powder containing cerium, aluminum and lanthanum; In the step of firing the raw material obtained by mixing in an inert gas or a non-oxidizing gas to form a general formula: Si _6-z Al _z O _z N _8-z :Eu (β<z<4.2) β-type lanthanum aluminum oxynitride; an annealing step of annealing the generated β-type lanthanum aluminum oxynitride; and an acid treatment step, which is annealed The β-type lanthanum aluminum oxynitride is immersed in the acid solution; the annealing treatment is performed under a reducing gas atmosphere selected from the group consisting of hydrogen or a mixed gas of hydrogen and argon, and the gas ambient pressure is 1 kPa or more and 10 MPa or less, and the gas ambient temperature is 1200 ° C or more and 1600 ° C or less, and the treatment time is 1 hour or more and 24 hours or less. The method for producing a β-type lanthanum aluminum oxynitride according to the first aspect of the invention, wherein the reducing gas atmosphere is a mixed gas of hydrogen and argon, and the concentration of hydrogen in the mixed gas is 1% by volume or more. The method for producing a β-type lanthanum aluminum oxynitride according to the first aspect of the invention, wherein the acid solution of the acid treatment step contains at least a mixed acid of hydrofluoric acid and nitric acid. The method for producing a β-type lanthanum aluminum oxynitride according to claim 2, wherein the acid solution of the acid treatment step contains at least hydrofluoric acid Mixed acid with nitric acid. The method for producing a β-type lanthanum aluminum oxynitride according to any one of claims 1 to 4, wherein the firing is carried out in a gas atmosphere at a temperature of 1850 ° C or higher.